Watercraft are often powered by an outboard motor positioned at a stern of the craft. The outboard motor has a powerhead and a water propulsion device, such as a propeller. The powerhead includes a cowling in which is positioned an internal combustion engine, the engine having an output shaft arranged to drive the water propulsion device.
Generally, the motor is connected to the watercraft in a manner which permits the motor to be "trimmed" up and down. For example, the motor may be connected through a horizontally extending pivot pin to a clamping bracket which attaches to the watercraft. In this manner, the motor may be moved in a vertical plane about the axis of the pin. This allows an operator of the watercraft to raise the propeller out of the water of place it deep in the water dependent upon the trim angle of the motor.
In addition, the motor is arranged to turn left and right about a generally vertically extending axis. This arrangement permits the operator of the watercraft to change the propulsion direction of the motor, and thus change the direction in which the watercraft is propelled.
The size of the motor, especially the powerhead portion which includes the motor, effects the air drag associated with the watercraft. It is desirable for the motor to have a small profile to reduce the air drag. In addition, it is generally desirable for the engine to be compact, since this makes the task of trimming and turning the motor less difficult.
The engine typically is of the internal combustion type with one or a plurality of cylinders. Internal combustion engines typically incorporate reciprocating piston in the cylinders. The engines typically operate on the two or four stroke principal. In either of the two or four stroke cycle there is a compression stage where the piston is compressing the fuel and air mixture within the cylinder before the ignition system is triggered. During this compression stroke some of the fuel and air mixture passes or "blows" by the piston seal ring and then travels to the crankcase chamber. A portion of the fuel and air mixture also blows-by the valve seat and into the chamber surrounding the camshafts.
As the engine operates, more of the fuel and air mixture builds and accumulates in crankcase and the area surrounding the camshaft. In order to increase the efficiency of the engine as well as decrease the emissions of the motor is it desirable to capture the blow-by gas and route it back to in the intake system of the motor.
A need therefore exists to increase the efficiency of the engine. Further, a need exists to improve the emissions of the engine.
Once the blow-by gas is in the crankcase chamber and the area surrounding the cam shaft it is exposed to the engine oil. Once exposed to the engine oil, the fuel and air mixture combines with the engine oil. Allowing the mixture of engine oil and the fuel and air mixture back into the combustion chamber is undesirable as it will decrease the engine performance as well as increase the emission output.
A need therefore exists for a blow-by gas arrangement that separates the fuel and air mixture from the engine oil.
One solution for this problem is shown in FIG. 14. In FIG. 14 a schematic engine is shown with an engine 26, including crankcase chamber 418 and a camshaft chamber 400 with a blow-by gas passage 404 therebetween. The engine 26 also includes an oil pan 412 to capture the engine oil before it is returned to the galleries where it is used to lubricate the crankshaft and camshaft. Further, the engine contains a breather element 432 to separate the engine oil from the blow-by fuel and air mixture. In this design, the breather element 432 is adjacent to the cam chamber 400 so as too minimize the overall height of the engine to minimize air drag. A problem with this design, however, is that too much of the engine oil is put into the breather element. Therefore, engine oil is being sent into the combustion chamber thereby decreasing engine performance. Furthermore, the engine oil is burning in the combustion process and is increasing the emissions thereby creating smoke and an undesirable smell.
A need therefore exists to improve the arrangement of the components of the engine in order to maintain increase engine performance as well as improve engine exhaust emissions.